Komatsu PC75UU-2 Injection Pump Timing

[Smedlow]

My 1994 PC75UU-2, Serial number 8310, Engine Model # 4D95L-1, was belching black smoke and spilling fuel into the crankcase. Air filter was clean. Started well, ran well, but smoked under even a light load. Injectors were just rebuilt. Decided it was the Injection Pump. Took it off, sent it away and had it rebuilt and the shop said it was bad. Got the rebuilt pump back and installed it. Tried to time it like the book said.....Take out the spring from the valve holder and hand pump while moving the pump away from and toward the engine block. It's supposed to be timed when the flow stops. The flow never stopped. Turn engine over and try again....still no flow stoppage.

Finally, I put it all together and set the pump where it had been before and tried the starter. It started, but still isn't timed. Is there a way to dynamically time it with a timing light? The marks on the crank pulley line up with the timing pointer and, though they're hard to read, look like 8 before, a series of gradations, 4 before, and then a space and a single mark. I tried the timing on the single mark.

What am I doing wrong? Probably plenty, but I would be grateful for advice. Thanks.

 

[Smedlow]

I started it again today and it seemed to run fine. I looked at the side of the pump and the plate it mounts to and found a hash mark on both. I was running it about 1/8" misalignment between the hash marks. I moved the pump to align the marks and tightened it down. It started fine and seemed very normal. I can't see that there the alignment of the two marks does anything except to get close. It seems that real timing needs to be a customized alignment between the crankshaft and the pump delivery. Any thoughts?

 

[John C.]

That's all it takes on the engines before electronics. Pulling out the check valve and fuel timing them was only when you didn't have the mounting marks. It works but you have to turn the engine real slow while pumping on the primer pump. It's a pain so I used to put scratch or chisel marks on the flanges before I removed the pump.

 

[Smedlow]

Just because nothing goes as smoothly as it should, I started the motor and let it run to check for leaks. Sure enough, there was a leak running down the plate at the front of the pump. I looked at the book to see what might be leaking and saw that an o ring goes around the nose of the pump. I didn't remember an o ring on there placed by the rebuilder, and I found the old one in the bucket of bolts from disassembly. I finally decided that I had to take the pump off again to check for the o ring, so I did. The good news was that I'm much faster the second time, and I only took apart what I had to. No o ring. I put it back together with o ring in place and it doesn't leak and runs great. No smoke!. I put the counter weight back on and buttoned it up. Now I need to deal with the track......a few of the links are bad. Thanks for your advice.

 

[John C.]

I don't know how many times I've run into people who would have just not done anything about the leak and whined for month on end about it.
Nice work!